1. Field of the Invention
The present invention relates to extruded, modular panels for use in the construction of walls, ceilings, and the like in buildings, which panels may be either opaque or light-transmitting.
2. Description of the Related Art
Plastic insulative panels are known in the art, and commonly consist of two spaced-apart extruded sheets of a plastic material constituting major surfaces of the panels, integrally connected by ribs perpendicularly or obliquely oriented with respect to the sheets, producing a plurality of air spaces having a rectangular cross-section. Similarly constructed panels also include an intermediate sheet, thus forming two enclosed spaces between the major surfaces.
In U.S. Pat. No. 4,573,300, there is also disclosed a further type of panel, wherein the ribs zigzag between the two major surfaces and are attached to them via short auxiliary ribs, which extend from the inflection points of the zigzagging main ribs to the respectively nearest one of the major surfaces. The purpose of this arrangement is to reduce to a minimum the mass of material at the point of attachment of the ribs to the major surfaces. At the same time, these auxiliary ribs being relatively short, the structural reinforcement effect of the main ribs remains substantially unimpaired.
All of the above-described prior art panels having generally only two, or at most three, enclosed spaces, are formed with the major surface, which is adapted to face the outside, having a thickness greater than the thickness of the other major surface, for the purpose of withstanding buckling. Furthermore, in order to enhance the strength of such panels to withstand pressures, such as wind pressures applied thereupon, the areas bracketing both sides of the connection between a rib and the major surface adapted to face the outside of the structure, have a substantially thicker cross-section, projecting towards the interior of the panel. This forms arch-like spaces adjacent to the outwardly facing major surface, thereby increasing the overall cost of the extrusion head and the cost of the panel due to the added reinforcing material used, not to mention the added material and weight.
Prior art panels are also formed such that an internal support structure is formed in a manner that all of the support walls are normal to the two major surfaces to form chambers normal to the major surfaces. The internal support structure is formed separate from the two major surfaces. After forming, the internal support structure is fixed by gluing between the two major surfaces, which are separately formed.